Disk drive devices are already known which utilize a magnetic force to clamp a removable disk when the disk is mounted on a turntable rotated by a motor.
As shown in FIG. 3, in these disk drive devices, a clamping magnet 112 is fittingly assembled around an outer peripheral portion of a boss portion 111 of a turntable 110 fixed to a rotating shaft 118 of a motor 117. A disk mounting portion 113 on which a disk 115 is mounted is placed in an outer peripheral portion of the turntable 110. To be placed in the disk drive device, the disk 115 is mounted on the disk mounting portion 113. A magnetic material 116 such as a metal plate disposed in a cassette or the like (or a clamp device provided together with the disk drive device) for the disk 115 is then attracted by the magnetic force of the clamping magnet 112 to sandwich the disk 115 between the disk mounting portion 113 of the turntable 110 and the magnetic material 116. The disk 115 is thus clamped so as not to slip or liberate with respect to the turntable 110 when rotated. The disk is held in a stable posture. In the conventional disk drive device, an area in which the clamping magnet 112 is disposed is different from an area in which the disk mounting portion 113 is provided; the areas are individually provided.
There has been a demand for miniaturization of these disks and disk drive devices. Instead of having the turntable provided separately from the motor, a configuration in practical use which enables a reduction in the thicknesses of the disk and the disk drive device has a disk mounting portion formed on a rotor frame constituting an outer portion of a rotor of the motor so that the rotor frame itself can also be used as the turntable. This allows the motor and the turntable to be formed using only one part, enabling a reduction in the number of parts required and in the thickness of the device.
An optical disk drive device disclosed in JP10-3740A has been proposed as a configuration that not only allows the motor and the turntable to be formed using only one part but also achieves simplification. As shown in FIG. 4, JP10-3740A proposes that in the optical disk drive device, a whole rotor frame 120 on which a boss portion 121 and a turntable portion (disk mounting portion) 122 are provided be integrally formed of a magnetic material such as a plastic magnet. The optical disk drive device is configured so that the disk 115 is placed on the turntable portion 122 formed on the rotor frame 120, having a magnetic function as the clamping magnet.